Download or read book Oceanic Lithosphere Magnetization written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2007.
Download or read book Oceanic Lithosphere Magnetization Marine Magnetic Investigations of Crustal Accretion and Tectonic Processes in Mid Ocean Ridge Environments written by and published by . This book was released on 2007 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin of symmetric alternating magnetic polarity stripes on the seafloor is investigated along East Pacific Rise (EPR) (9 degrees 25' -9 degrees 55'N) and Kane Megamullion (KMM) (23 degrees 40'N) in the Atlantic. At the EPR, along-axis variations in the axial magnetic anomaly result from changing source layer thickness, consistent with observed changes in seismic Layer 2a. The extrusive basalts therefore constitute the magnetic source layer along the ridge axis and long term crustal accretion patterns are reflected in the axial anomaly appearance. At KMM the C2r.2r/C2An. 1n (approx. 2.581 Ma) polarity reversal boundary is recorded by lower crust (gabbro) and upper mantle (serpentinized peridotites) rocks exposed on the seafloor by detachment faulting. Both lithologies have stable remanent magnetization, capable of contributing to the magnetic source layer. The geometry of the polarity boundary in the northern KMM region, interpreted to be a gabbro pluton, dips away from the ridge axis and is consistent with a rotated conductively cooled isotherm. In the central region the boundary in the serpentinized peridotites dips towards the ridge axis and is thought to represent an alteration front. The linear appearance of the polarity boundary across the two regions suggests that both lithologies acquired their remanence at approximately the same time.
Download or read book Diversity of Hydrothermal Systems on Slow Spreading Ocean Ridges written by Peter A. Rona and published by John Wiley & Sons. This book was released on 2013-05-02 with total page 1110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Published by the American Geophysical Union as part of the Geophysical Monograph Series, Volume 188. Diversity of Hydrothermal Systems on Slow Spreading Ocean Ridges presents a multidisciplinary overview of the remarkable emerging diversity of hydrothermal systems on slow spreading ocean ridges in the Atlantic, Indian, and Arctic oceans. When hydrothermal systems were first found on the East Pacific Rise and other Pacific Ocean ridges beginning in the late 1970s, the community consensus held that the magma delivery rate of intermediate to fast spreading was necessary to support black smoker-type high-temperature systems and associated chemosynthetic ecosystems and polymetallic sulfide deposits. Contrary to that consensus, hydrothermal systems not only occur on slow spreading ocean ridges but, as reported in this volume, are generally larger, exhibit different chemosynthetic ecosystems, produce larger mineral deposits, and occur in a much greater diversity of geologic settings than those systems in the Pacific. The full diversity of hydrothermal systems on slow spreading ocean ridges, reflected in the contributions to this volume, is only now emerging and opens an exciting new frontier for ocean ridge exploration, including Processes of heat and chemical transfer from the Earth's mantle and crust via slow spreading ocean ridges to the oceans The major role of detachment faulting linking crust and mantle in hydrothermal circulation Chemical reaction products of mantle involvement including serpentinization, natural hydrogen, abiotic methane, and hydrocarbon synthesis Generation of large polymetallic sulfide deposits hosted in ocean crust and mantle Chemosynthetic vent communities hosted in the diverse settings The readership for this volume will include schools, universities, government laboratories, and scientific societies in developed and developing nations, including over 150 nations that have ratified the United Nations Convention on the Law of the Sea.
Download or read book Advanced Geophysical Studies of Accretion of Oceanic Lithosphere in Mid Ocean Ridges Characterized by Contrasting Tectono magmatic Settings written by Min Xu (Ph.D.) and published by . This book was released on 2012 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of the oceanic lithosphere results from magmatic and extensional processes taking place at mid-ocean ridges (MORs). The temporal and spatial scales of the variability of these two processes control the degree of heterogeneity of the oceanic lithosphere, represented by two end-member models: the classical Penrose Model exemplified by layered magmatic crust formed along fast-spreading MORs, e.g., East Pacific Rise (EPR); and the recently defined Chapman Model describing heterogeneous mafic and ultramafic lithosphere formed in settings of oceanic detachment faulting common along slow-spreading MORs, e.g., Mid-Atlantic Ridge (MAR). This thesis is using advanced marine geophysical methods (including finite-difference wave propagation modeling, 3D multi-channel seismic reflection imaging, waveform inversion, streamer tomography, and near-bottom magnetics) to study lithospheric accretion processes in MORs characterized by contrasting tectono-magmatic settings: the magmatically dominated EPR axis between 9°30'-10°00°N, and the Kane Oceanic Core Complex (KOCC), a section of MAR lithosphere (23°20°-23°38°N) formed by detachment faulting. At the EPR study area, I found that the axial magma chamber (AMC) melt sill is segmented into four prominent 2-4-km-long sections spaced every -5- 10 km along the ridge axis characterized by high melt content (>95%). In contrast, within the intervening sections, the AMC sill has a lower melt content (41-46%). The total magma volume extracted from the AMC sill was estimated of ~46 x 106 M3, with ~24 x 106 M3 left unerupted in the upper crust as dikes after 2005-06 eruption. At the KOCC, I used streamer tomography to constrain the shallow seismic velocity structure. Lithological interpretation of the seismic tomographic models provides insights into the temporal and spatial evolution of the melt supply at the spreading axis as the KOCC formed and evolved. Investigation of a magnetic polarity reversal boundary in crosssection at the northern boundary of KOCC suggests that the boundary (representing both a frozen isotherm and an isochron) dips away from the ridge axis along the Kane transform fault scarp, with a west-dipping angle of ~45° in the shallow (
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2008 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advanced Geophysical Studies of Accretion of Oceanic Lithosphere in Mid ocean Ridges Characterized by Contrasting Tectono magmatic Settings written by Min Xu and published by . This book was released on 2012 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of the oceanic lithosphere results from magmatic and extensional processes taking place at mid-ocean ridges (MORs). The temporal and spatial scales of the variability of these two processes control the degree of heterogeneity of the oceanic lithosphere, represented by two end-member models: the classical Penrose Model exemplified by layered magmatic crust formed along fast-spreading MORs, e.g., East Pacific Rise (EPR); and the recently defined Chapman Model describing heterogeneous mafic and ultramafic lithosphere formed in settings of oceanic detachment faulting common along slow-spreading MORs, e.g., Mid-Atlantic Ridge (MAR). This thesis is using advanced marine geophysical methods (including finite-difference wave propagation modeling, 3D multi-channel seismic reflection imaging, waveform inversion, streamer tomography, and near-bottom magnetics) to study lithospheric accretion processes in MORs characterized by contrasting tectono-magmatic settings: the magmatically dominated EPR axis between 9°30'-10°00'N, and the Kane Oceanic Core Complex (KOCC), a section of MAR lithosphere (23°20'-23°38'N) formed by detachment faulting. At the EPR study area, I found that the axial magma chamber (AMC) melt sill is segmented into four prominent 2-4-km-long sections spaced every ~5- 10 km along the ridge axis characterized by high melt content (>95%). In contrast, within the intervening sections, the AMC sill has a lower melt content (41-46%). The total magma volume extracted from the AMC sill was estimated of ~46 × 106 m3, with ~24 × 106 m3 left unerupted in the upper crust as dikes after 2005-06 eruption. At the KOCC, I used streamer tomography to constrain the shallow seismic velocity structure. Lithological interpretation of the seismic tomographic models provides insights into the temporal and spatial evolution of the melt supply at the spreading axis as the KOCC formed and evolved. Investigation of a magnetic polarity reversal boundary in crosssection at the northern boundary of KOCC suggests that the boundary (representing both a frozen isotherm and an isochron) dips away from the ridge axis along the Kane transform fault scarp, with a west-dipping angle of ~45° in the shallow (
Download or read book Processes of Magmatic and Tectonic Accretion of Oceanic Lithosphere at Mid ocean Ridges written by Anke Dannowski and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Implications of Fine Scale Magnetics for the Structure and Evolution of Slowly Accreted Oceanic Crust written by and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The long range objective of this program is to understand the structure of oceanic crust created at slow-spreading ridges by investigating the patterns of magnetization that reside in the crust. The project seeks to investigate how crustal magnetic fields are related to the structural deformation history of oceanic crust formed in slow spreading environments and how magnetization may be used to predict the properties of the underlying crust. Scientific Objectives are: (1) Investigate the relationship between crustal magnetization and the tectonic structure and architecture of oceanic crust by comparing the magnetization patterns of crust created at 'inside corners' versus 'outside corners' of ridge segment offsets. (2) Investigate the relationship between crustal magnetization and cyclic magmatic and tectonic processes involved in crustal formation and how this magnetization signal varies with age. (3) Investigate along-axis variability in crustal magnetization within a ridge segment and compare with the ridge axis signal. (4) Map magnetic isochrons to provide temporal framework for other related studies e.g. investigate how crustal structure and seafloor morphology change with spreading rate.
Download or read book Faulting and Magmatism at Mid Ocean Ridges written by W. Roger Buck and published by American Geophysical Union. This book was released on 1998-02-04 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book can benefit the nonspecialist who wants to keep up with work on magmatism and tectonics, as well as researchers working on mid-ocean ridges."--BOOK JACKET.
Download or read book Anomalous Magnetic Field of the World Ocean written by Alexander M. Gorodnitsky and published by CRC Press. This book was released on 1994-10-12 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book investigates the anomalous magnetic field of the ocean and its connection with geological structure, tectonic evolution of the oceanic lithosphere, and magnetic properties of different rock types in the oceanic crust. The book describes new instruments and techniques of gradient magnetic measurements with three sensors, as well as the new technique of processing and interpretating hydromagnetic data on the basis of adoptive filtration and reparametrization. The text provides unique data of geomagnetic surveys carried out by Russian research vessels in different regions of the World Ocean, including submersible apparatus and ingenious theoretical and experimental technology of the magnetic modeling and investigations of the nature of magnetic anomalies. The results of systems analysis of geochemical content and composition during the mid-oceanic ridge basalt are presented.
Download or read book Processes of Magmatic and Tectonic Accretion of Oceanic Litosphere at Mid Ocean Ridges written by Anke Dannowski and published by . This book was released on 2009 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book New Insights Into Accretion and Cooling of Lower Ocean Crust at Ultraslow and Fast spreading Mid ocean Ridges written by Christopher James Doorn and published by . This book was released on 2022 with total page 598 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mid-ocean ridges are the primary divergent tectonic margins and generate the ocean crust, which covers ~60% of Earth’s surface. The gabbroic lower ocean crust hosts lithologic and structural diversity varying with spreading rate and magma supply. This dissertation examines lower crustal accretion at ultraslow- and fast-spreading ridges to better constrain crustal accretion and cooling across spreading rates. Trace element compositions of zircon from Atlantis Bank (Southwest Indian Ridge) characterize the final stages of magmatism and the thermal architecture in the lower crust produced along an ultraslow-spreading ridge. U-Pb zircon dates of evolved gabbroic rocks from the fast-spread lower crust at Pito Deep (East Pacific Rise) reveal significant off-axis magmatism, implying locally robust magmatism and relatively slow cooling of this nascent ocean crust. Textural characteristics of gabbroic rocks from Pito Deep highlight the lateral complexity of the fast-spread lower crust, and record increasing degrees of magmatic strain with depth. Synthesizing textural data, U-Pb geochronology, mineral chemistry, and magnetic data from Pito Deep supports a pulsed gabbro glacier flow process for generating the lower ocean crust at magmatically robust fast-spreading ridges.
Download or read book Geophysics Tectonics Abstracts written by and published by . This book was released on 1987 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aquatic Sciences and Fisheries Abstracts written by and published by . This book was released on 1992 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book InterRidge News written by and published by . This book was released on 2003 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Encyclopedia of Geomagnetism and Paleomagnetism written by David Gubbins and published by Springer Science & Business Media. This book was released on 2007-07-19 with total page 1061 pages. Available in PDF, EPUB and Kindle. Book excerpt: This reference encompasses the fields of Geomagnetism and Paleomagnetism in a single volume. Both sciences have applications in navigation, in the search for minerals and hydrocarbons, in dating rock sequences, and in unraveling past geologic movements such as plate motions they have contributed to a better understanding of the Earth. The book describes in fine detail the current state of knowledge and provides an up-to-date synthesis of the most basic concepts. It is an indispensable working tool not only for geophysicists and geophysics students but also for geologists, physicists, atmospheric and environmental scientists, and engineers.
Download or read book Some Aspects of the Structure and Magnetization of the Oceanic Crust written by Roi Granot and published by . This book was released on 2009 with total page 97 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure and magnetization of the oceanic crust reflect its tectonic and magmatic evolution since its initial formation. The magnetization of the crust also provides a record of the polarity reversals and strength of the Earth's geomagnetic field. In this dissertation I first describe absolute paleointensity measurements made on gabbroic rocks collected from the lower oceanic crust of the Troodos ophiolite, Cyprus. The resultant data-set provides a view into the geomagnetic field during the end of the Cretaceous normal polarity superchron (CNS, 120.6 to 83 million years ago). This data-set is then compared to the locally and globally existing data and predictions made by geodynamo numerical simulations. The results hint that the geomagnetic field had similar properties during times of frequent reversals and times of stable polarity. The second chapter of this dissertation is focused on the marine magnetic anomalies observed across the North Pacific fracture zones. Here I analyze archival and newly collected magnetic anomaly and bathymetric profiles measured across three fracture zones in the Cretaceous Quiet Zone (CNS in age). Forward and inverse modeling indicate that these anomalies arise from remanent magnetization, with enhanced remanence located on one side of each fracture zone. These long-duration enhanced zones require some long-lived asymmetry in crustal construction processes near ridge-transform intersections. The calculated magnetization contrasts provide long-term constraints on the properties of the geomagnetic field during the Cretaceous superchron. Finally, using seismic reflection and magnetic anomaly grids collected in the Adare Basin, Antarctica, I explore the kinematic evolution of the West Antarctic rift system during the Neogene. Correlation of the Adare seismic sequence to the closest drillholes and the Ross Sea seismic stratigraphy establishes the temporal framework of three regional tectonic events. Overall, minimal but significant extensional activity took place in the Adare Basin after seafloor spreading stopped. Comparison of the results with observations from the central and southern parts of the rift system suggests that a major change in plate motion took place in the middle miocene.
